Production of ketones



Patented Feb. 26, 1952 UNITED STATES PRODUCTION OF .KETONES- Gennajdy Kosolapoif, Auburn, -Ala., assignor to Monsanto Chemical Company, St. Louis, :Mo., a corporation of Delaware NuDrawh g. Application-December,l4,..1950, fierial No. 200,879

e'Claims. I

This invention relates to the production of arematio ketones by axnovel method and more particularly to certain .ketcnes not obtainable by prior methods.

A present object is to provide amethod Jtoiobtain .acetophenone derivatives useful in perfmnery. In the .case of the higher molecular weight compounds, the products may also "be used as plasticizers. An object is also to prepare diacetyl derivatives of aryl compounds. such products have not been generally obtainable by prior art methods such .::as the Friedel-Crafts reaction.

Another object of the invention is to prepare .acetophenones "which may be transformed into various vinyl compounds. Other objects will .be apparent Irom theiollowing description.

Acetophenone .and its derivatives "have "been alkyl group. When there are two alkyl substituprepared .by a number of methods, but thejprior methods have been characterized by high costs, because of the numerous steps involved and the expensive catalysts necessary. Acetophenones have also been made by the'Friedel-Crafts reaction, but the present invention dispenses :with the use of the more expensive acid-anhydrides and halides heretofore -necessary; "instead, "the cheaper acids maybe used directlyto manufacture the mono-acetyl derivatives. "In -addition the poly-acetyl'ated aromatic compounds,

not obtainable by'prior art methods, may now 2 also be prepared. 1 I have 'now foundthat aromatic -ketones may be prepared by reaction of carboxylic acids with alkyl substitutedaromatic compounds'in the .presenceof phosphorus pentoxide. The alkyl radical may have from 1 to 18-carbon atoms'and'may be primary, secondary or tertiary in character. 'There' may be one or more alkyl groups up to three per aromatic ring. I

Examples of suitable alkyl substituted aromatic compounds are the following: toluene, "ortho meta-, or parax y lene, mesitylene, mono-, dior triethylbenzene, n-propylbenzene, cumene, paracymene, n-butylbenzene. 'secondary'butylbenzene. tertiary butvlbenzene, ycyclohexylbenzene, octylbenzene, dodecylbenzene, octadecylbenzene.

suitable -.carboxylic .acids may .be any of the monobasic aliphatic carboxyl'ic acids'having more than 2 carbon atoms in the'molecule, such. for examplepas acetic, propion i floutyric, "val'eric, caproic, heptyl-ic, caprylic, pelargonic, capric, lauric, myristic. palmitic, stearic, oleic, arachidic,

.behenic, lignoceric, cerot'ic, etc.

I The general "reaction'appearsto proceed as indicated by the equation:

pheric pressure.

ents in the ring in para-position the carbonyl subs'tituent enters at the 2- or 5-position. When there is substitution of two carbonyl substituents 'thesubsti'tution occurs mainly at the 2- and 5 position. "Where there is substitution of more than one carbonyl -'substituent, a mixture of monoand di-carbonyl substituted aromatic compounds .is produced. This mixture can be resolved usually by careful fractional distillation.

The invention 'is' best ,carried out by mixing the ingredients in the proportions required for the production of the desired compound. The

mixture is heated to accelerate the .reaction.

Conveniently it may be heated to the refluxing temperature of the acid-hydrocarbon mixture. Refiuxing may take place at ordinary atmos- However, temperatures other than that provided for by atmosphere temperature refluxing'may also be employed. The reactivity of the alkyl aromatic body will vary directly with thenumber of 'alkyl 'substituents present. Thus, a dialkyl substituted aromatic compound is more reactive than a mono-alkyl compound anda tr'ialkyl compound is more active than the dialkyl derivative. symmetrically disposed alkyl substituents on the benzene ring are more reactive than unsymmetrical ones. Accordingly, the temperature to which the reaction mixture is heated should be varied, depending :upon the "type of compound undergoing reaction and the time during which reaction is to be completed. In general, lower temperatures require longer times of reaction.

"Since thePziOe *is'required tobe present in the reaction, it is desirable that it be intimately disp'ersed therein. Fortunately, P205 is obtainable as :a'ifin'ely divided solid which, 'when dry,

is. readilyidispersed'"by' eflicient stirring. However, water is liberated during the reaction'or may be present insmall quantities in the reactants which will combine with the P205 to form metaphosphoric acid. The phosphoric acid :so formed is asticky or :gummy substance which is diificult to disperse itself .and when presentin substantial amounts will tend to occlude dry P205, making it more or less unavailable to the reactants. For this reason I prefer to have present a further dispersing agent which should be an inert material. For this purpose I may employ any inert solid or liquid. Solid dispersing agents which are useful for the present purpose are finely divided forms of silica, such as diatomaceous earth, finely ground quartz, finely divided silica gel, silica aerogel, etc. The amount of silica employed will depend upon the amount of water liberated and the amount of P205 present. In general, it is desired to utilize only sufiicient P205 necessary to combine with the water liberated by the reaction so as to form metaphosphoric acid therewith. However, it is not always possible to completely react all of the P205 employed by reason of mechanical difficulties in dispersing this substance. However, by employing a finely divided inert material in conjunction with'the P205 a better economy of P205 is realized.

My invention is further illustrated by meansof the following examples:

Example 1' Meta-xylene (106 g., 1.0 mole) and glacial acetic acid (60 g, 1.0 mole) were mixed in a flask equipped with a stirrer and a reflux condenser 7 With the protected by a calcium chloride tube. stirrer in operation, 3 g. of Celite filter aid (a diatomaceous form of practically pure silica) was added to the mixture, followed by 71 g. phosphorus pentoxide (0.5 mole). and refluxing for two hours was sufiicient for reaction. It was noted that the mixture first coagulated temporarily to a viscous mass and then began to liquefy and remain-quite fluid because of the presence of the dispersing filter aid. On cooling, the organic layer was decanted from the semi-solid inorganic matter, which was extracted to obtain an increment of the organic product. Distillation of the final product, under reduced pressure, gave 52 g. of 2,4-dimethyl acetophenone as a colorles liquid, B. P. 120-5/20 mm. and 10 g. of dimethyl diacetylbenzene as a rapidly crystallizing oil, B. P. l-150/5 mm.

Example 2 The preceding example was repeated using a 30-minute reaction period to yield 53 g. dimethyl acetophenone and 12 g. dimethyl diacetylbenzene.

Example 3 dation in 95% yield to 2,4-dimethyl benzoic acid,

M. P. 125.2 from hot water.

The dimethyl diacetylbenzene fractions were combined and recrystallized from alcohol to yield the compound as colorless needles, M. P. 123.5- 124.

Example 4 The preceding procedure was applied with toluene (92 g., 1.0 mole) glacial acetic acid (60 g., 1.0 mole) and phosphorus pentoxide ('71 g., 0.5 mole) with 3 g. or Celite. Reaction for two hours yielded methyl acetophenone, B1 1 ll5-2Q/20 mm.

Vigorous stirring Example 5 Cyclohemylbenzeria-A run analogous to the toluene run gave as a high boiling oil, cyclohexyl acetophenone, B. P. 150-60/ 10 mm.

Example 6 Mesitylene.l00 g. of mesitylene, 120 g. of glacial acetic acid, '71 g. of phosphorus pentoxide I and 5 g. of Celite gave, after a 90-minute reaction,

g. of acetomesitylene, B. P. -2/ca. 4 mm. for an 82.5% yield.

Example 8 Propionic acid.100 g. of meta-xylene, 25 g. of propionic acid and 25 g. of P205 were mixed in the presence of 3 g. of Celite using stirring at reflux temperature for one hour. After recovery of unused xylene, this reaction gave 19 g. of 2,4-di: methyl propiophenone, B. P. -20/16 mm. and 15 g. of higher boiling dipropionyl derivatives of the phosphoric acid.

Example 9 Stearic a.cid.--100 g. of meta-xylene, 20 g. of stearic acid, 10 g. of P205 and 3 g. of Celite were stirred at reflux for 2% hours. The products were, after distillation to remove excess xylene and stearic acid, '3 g. of 2,4-dimethyl stearophe'- none, B. P. 250-70/15 mm.,' M. P. 40. A further portion of the reaction product consisted of higher boiling point derivatives.

This application is a continuation-in-part of my application Serial No. 679,559, filed June 26, 1946, now abandoned.

WhatIclaim is:

1. The process which comprises reacting an alkyl substituted aromatic compound, said aromatic compound containing not in excess of 3 alkyl substituents with an aliphatic monocarboxylic acid in the presence of phosphorus pentoxide.

2. The process which comprises reacting toluene with an aliphatic monocarboxylic acid in the presence of phosphorus pentcxide.

3. The process which comprises reacting xylene with an aliphatic monocarboxylie acid in the presence of phosphorus pentoxide.

4. The process defined in claim 2, in which the aliphatic monocarboxylic acid 'is acetic acid.

5. The process defined in claim 3, in which the aliphatic monocarboxylic acid is acetic acid.

. GENNADY M. KOSOLAPOF'F.

REFERENCES CITED The following references are of record in the file of this patent: V

UNITED STATES PATENTS Number Name Date 2,238,594 Malishev Apr. 15, 1941 FOREIGN PATENTS Number Country Date 316,750. Great Britain Aug. 8, 1929 

1. THE PROCESS WHICH COMPRISES REACTING AN ALKYL SUBSTITUTED AROMTIC COMPOUND, SAID AROMATIC COMPOUND CONTAINING NOT IN EXCESS OF 3 ALKYL SUBSTITUENTS WITH AN ALIPHATIC MONOCARBOXYLIC ACID IN THE PRESENCE OF PHOSPHORUS PENTOXIDE. 